U.S. Pat. No. 3,223,443 of George W. Misson discloses a method and apparatus for handling a flat or curved heated glass sheet without physical contact between the glass sheet and a downwardly facing support bed. The apparatus of the Misson patent is merely disclosed as supporting a glass sheet without any disclosure of specific utility in any glass sheet processing operation. Only relatively small glass sheet samples, e.g. 4 inches square, were supported by the Misson apparatus after being placed in position by hand which clearly indicates the apparatus was merely experimental without any industrial application.
One embodiment of the Misson patent apparatus includes inverted cup shaped modules that are spaced from each other to establish pressure and exhaust zones adjacent the top surface of the glass sheet to be supported. This establishes flows of gas to and from the zones directly above the glass sheet at a location between the glass sheet and the support bed. Control of the rates at which the gas is emitted and exhausted differentially establishes a net pressure directly above the glass sheet that is less than the ambient pressure by an amount equal to the weight of the sheet. The support bed supports either unheated glass sheets or glass sheets which have been preheated to a deformation temperature. The glass sheet may be initially supported beneath the bed on a flat, uniform preheated surface. Thereafter, the physical support for the glass sheet is removed.
Another embodiment of the Misson patent apparatus includes a support bed having a porous bottom plate through which gas under pressure is supplied. Tubes that extend through the porous plate provide for the withdrawal of gas to reduce the pressure above the glass sheet.
U.S. Pat. No. 4,282,026 of Harold A. McMaster, Normal C. Nitschke, and John S. Nitschke discloses apparatus for bending glass sheets wherein a heated glass sheet is received from a horizontal conveyor by direct engagement with a downwardly facing surface of a vacuum holder and is thereafter deposited by the holder onto a curved mold on which bending of the heated glass sheet takes place. A differential gas pressure preferably provided by a vacuum drawn through holes at the downwardly facing surface secures the glass sheet to the holder as it is moved from the conveyor to the bending mold. A sheet-like cover is provided on the surface and has a porous construction, such as is provided by matted silica fibers, in order to distribute the vacuum and prevent marring and scratching of the heated glass sheet surface engaged by the holder. Also, the direct engagement of the glass sheet with the sheet-like cover results in wear that requires periodic cover replacement.
U.S. Pat. No. 4,111,676 of Charles H. Mechling et al discloses glass sheet tempering performed on a roller conveyor between upper and lower arrays of nozzles through which quenching gas is supplied. In addition to lower rolls provided for conveying the glass sheets during the tempering, upper hold-down rolls are provided in case the quenching gas supplied by the lower nozzles lifts the glass sheet being tempered upwardly off the lower conveyor rolls. Driving of the upper hold-down rolls is also provided to perform conveyance of a glass sheet lifted off the conveyor rolls by the quenching gas from the lower nozzles.